ACSM Releases Expert Consensus Statement: The Biological Basis of Sex Differences in Athletic Performance

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ACSM Releases Expert Consensus Statement: The Biological Basis of Sex Differences in Athletic Performance

Sept. 29, 2023

(Indianapolis, IN)- September 29, 2023 – The American College of Sports Medicine (ACSM) has published an expert consensus statement in the September issue of its Translational Journal. Expert Consensus Statements provide a mechanism by which ACSM can address topics of high importance and/or with broad impact. 

The primary goal of this consensus statement, which focuses primarily on adult male and female athletes, is to contribute to the public dialogue by providing the latest scientific knowledge and subject matter expertise on the sex differences in athletic performance, while assisting with evidence-based solutions and ensure an equitable and fair solution for all.  

“This statement emerges from the hard work of thought leaders who convened to discuss sex differences in athletic performance using a blend of research evidence and consensus of expert opinion,” said lead author, Sandra Hunter, Ph.D., FACSM.  

Key findings of the statement are as follows:  

  • Biological sex is a determinant of athletic performance: adult males are faster, stronger, more powerful than females because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes.  

  • Before puberty, sex differences in athletic performance are minimal. Significant differences emerge at puberty (-12 years) due to anabolic effects of testosterone in males. Testosterone levels rise 20-30-fold in males during puberty and are 15 times higher in males than females by age 18. 

  • Direct and indirect effects of testosterone during male puberty include increase skeletal muscle mass due to larger muscle fiber cross-sectional area, especially fast, type II fibers; lower percentage body fat; higher hemoglobin concentration and mass; larger ventricular mass (heart) and cardiac volumes; larger airways and lungs; greater body height; and longer limbs. 

  • Adult males are stronger, more powerful, and faster than females of similar age and training status. The sex difference in athletic performance where endurance or muscular power is required is roughly 10-30% depending on the event. 

  • Past and present studies of athletic performance, acute exercise and exercise training involve the testing of more males than females or fail to distinguish between the sexes. Consequently, less is known about the physiology of female athletes than males, the limits of their athletic abilities, and the acute and adaptive response of females to exercise and training.  

  • The rate of improvement in athletic performance of women has exceeded that of men in the last 100 years across a multitude of sports as women have gained access to training, equipment, facilities, and opportunities. 

“It should be noted that ACSM acknowledges that there are gaps in the data and further research is needed to address them,” said Dr. Hunter. “A major step toward closing the knowledge gap is to include more and equitable numbers of women to that of men in mechanistic studies that determine any of the sex differences in response to an acute bout of exercise, exercise training and athletic performance.”  

This consensus statement is the first in a series of three ACSM pronouncements on the topic of sex differences and transgender athletes. 

Paper two, currently in development, will focus on clinical care (health/performance) issues of transgender athletes. The goal of this paper is to provide a systems-based approach for discussing the medical care of transgender athletes. The third paper in the series will be a call to action on the need for more research. The goal of this paper is to identify the next steps needed to address research (or knowledge) gaps identified in papers one and two. The publication of the call to action is also currently in development.  

To learn more about this pronouncement, read the full expert consensus statement. More resources can be found at

Media Contact: ACSM Chief Communications Officer Paul Branks

Correction Note (Published 10/6/23)

The Consensus Statement Writing Group has corrected two errors identified in the original pronouncement published on Sept. 29. Both errors were found in the same statement in Box 1: Definitions.

Original Statement

Two percent of humans are intersex, harboring both male and female reproductive organs, and are reproductively fertile.

Corrected Statement

Differences/disorders of sex development (DSD) are rare conditions in which the development of chromosomal, gonadal, and anatomic sex is atypical (outside the binary of male/female).

Rationale for Corrections

This statement erroneously shared that “Two percent of humans are intersex..” The two percent figure represents the broadest range of conditions characterized by genital, reproductive, hormonal or sex chromosome differences, and includes many conditions that are not widely considered to be classified as DSD/intersex traits. The prevalence is much lower with narrower definitions of DSD/intersex. As a result, the two percent figure has been removed, the phrase corrected and the language is now consistent with the original corresponding sentence in the consensus statement itself (See page 19, under the heading “Hormonal Disorders (PCOS, DSD)”).

Additionally, the sentence incorrectly stated that individuals with DSD are “reproductively fertile.” Because some with DSD do experience infertility, the phrase was removed completely.

The Translational Journal of the American College of Sports Medicine will release an errata as soon as possible in order to ensure the published record is as accurate as possible.

Medicine & Science in Sports & Exercise will incorporate the corrected language into the final version of the consensus statement, which will appear in its December 2023 issue.